The present invention relates to a high water-containing elastomer medical catheter, especially urinary catheter and to a process for preparing the same.
It has long been a clinical practice that medical catheter, especially urinary catheter, is made of hydrophobic polymeric materials such as rubber and plastics. The poor surface lubricity of the catheter often causes pains and sufferings due to contact and friction upon insertion into the body cavity. In addition to its high tendency of damaging the mucosal tissue, it may also bring about cross infection which may jeopardize the life of the patient. In order to improve its surface lubricity, the surface is usually overcoated with lubricant, which may not only lead to inconvenience to catheterization but also remain some of lubricants inside the body. This is detrimental to the health of the people, too.
In recent years, a wide variety of methods has been put forward and tried in order to reduce surface friction and provide excellent lubricity to the catheter, which is generally formed of a layer onto the surface of the conventional material with a hydrophilic polymer. For example, the method disclosed in U.S. Pat. No. 4,642,267, uses a simple blend of thermoplastic polyurethane and polyvinyl pyrrolidone (PVP) depositing onto the surface of the catheters. This coated layer does not adhere firmly to the plastic substrate, and it is easy to be stripped off when contacting water, physiological saline, urine or other body fluid worsening its surface lubricity. U.S. Pat. No. 5,160,790 proposes a new method in order to overcome the defects. The catheter made of polyurethane is dripped into a mixture of isocyanate, polyethylene glycol, PVP and halogenated hydrocarbon. After removing the solvent by evaporation and applying some other post-treatments, a catheter having hydrogel-coated surface is obtained, which has lasting lubricity when wetted with water. However, a major defect of the method is that in order to meet the needs of fluidity (low viscosity) during the coating process, a large amount of solvents which can dissolve all the components but do not react with any of them is needed. At present stage, the proper solvent to meet the needs can only be a low-boiling halogenated hydrocarbon, such as chloromethane, dibromomethane, chloroform, and dichloroethane. All these solvents are inflammable and poisonous, which must be recovered under strict conditions. This will add to the burden of safety and environment and also increase the production cost.
It is taught in other prior art that onto the surface of the catheter is graft-polymerized hydrophilic monomers by using low temperature plasma or irradiation. Even though these methods have overcome the problems of stripping of the hydrophilic coating, the technological process is generally long and the work is rather complicated, which is not helpful for lowering the production cost and construction investment. In addition, in a wide variety of literatures, high water-containing elastomer and high strength polyvinyl alcohol hydrogel and the production technique of the shaped articles have been described, such as the technique of vacuum dehydration (Japanese Kokai Patent SHOWA 57-13053, SHOWA 58-36630), the technique of repeated freezing [M. Nambu, Polymer Applications (Japan), 32, 523 (1983)], the technique of slow-thawing [S. H. Hyon, Y. Ikada, Report of the Poval Committee, No. 8391 (1983)] and the technique of gel spinning (Japanese Kokai Patent SHOWA 59-130314). However, up to the present day, no other prior art similar or close to the present invention in terms of the purpose of invention, technology, and use of product has been found.
Therefore, what is thirstily desired for is a medical catheter, especially urinary catheter, having excellent lubricity and readily available at a lower price.